Docs for developing plugins (#7475)

* docs(plugins): new developing plugins section

Creates new section called Developing Plugins in
the plugin section of the docs.

1. Some changes to the Development guide page
2. Converted defaults/editor mode blog post
to new page
3. Converted snapshots blog post to new page
4. Adds new code styleguide page
5. Updates to apps and datasources pages
6. Adds plugin.json schema

* docs(links): fixes broken links

Fixes broken links to other pages as
well as broken image links.

docs/sources/features/datasources/index.md

@@ -9,13 +9,16 @@ weight = 5
 +++
 
 # Data Source Overview
+
 Grafana supports many different storage backends for your time series data (Data Source). Each Data Source has a specific Query Editor that is customized for the features and capabilities that the particular Data Source exposes.
 
 
 ## Querying
+
 The query language and capabilities of each Data Source are obviously very different. You can combine data from multiple Data Sources onto a single Dashboard, but each Panel is tied to a specific Data Source that belongs to a particular Organization.
 
 ## Supported Data Sources
+
 The following datasources are officially supported:
 
 * [Graphite]({{< relref "graphite.md" >}})

docs/sources/features/datasources/prometheus.md

@@ -16,7 +16,8 @@ weight = 2
 Grafana includes support for Prometheus Datasources. While the process of adding the datasource is similar to adding a Graphite or OpenTSDB datasource type, Prometheus does have a few different options for building queries.
 
 ## Adding the data source to Grafana
-![](/img/v2/add_Prometheus.png)
+
+![](/img/docs/v2/add_Prometheus.png)
 
 1. Open the side menu by clicking the the Grafana icon in the top header.
 2. In the side menu under the `Dashboards` link you should find a link named `Data Sources`.
@@ -49,6 +50,7 @@ For details on Prometheus metric queries check out the Prometheus documentation
 - [Query Metrics - Prometheus documentation](http://prometheus.io/docs/querying/basics/).
 
 ## Templated queries
+
 Prometheus Datasource Plugin provides the following functions in `Variables values query` field in Templating Editor to query `metric names` and `labels names` on the Prometheus server.
 
 Name | Description
@@ -65,8 +67,8 @@ For details of `metric names` & `label names`, and `label values`, please refer
 You can create a template variable in Grafana and have that variable filled with values from any Prometheus metric exploration query.
 You can then use this variable in your Prometheus metric queries.
 
-For example you can have a variable that contains all values for label `hostname` if you specify a query like this
-in the templating edit view.
+For example you can have a variable that contains all values for label `hostname` if you specify a query like this in the templating edit view.
+
 ```sql
 label_values(hostname)
 ```
@@ -78,4 +80,4 @@ You can also use raw queries & regular expressions to extract anything you might
 When the `Include All` option or `Multi-Value` option is enabled, Grafana converts the labels from plain text to a regex compatible string.
 Which means you have to use `=~` instead of `=` in your Prometheus queries. For example `ALERTS{instance=~$instance}` instead of `ALERTS{instance=$instance}`.
 
-![](/img/v2/prometheus_templating.png)
+![](/img/docs/v2/prometheus_templating.png)