* Error page implimentation
* Update Browser Compatibility check to check Chrome, FF, IE, Edge, and Safai
* Update strings with proper edge version
* undo uneeded changes and move to go template.
* more unneeded additions
* eliminate js and add local triangle
* fix typo
* Correct debug logging of browser version
* Modify Browser Check to pass user_agent object only and write test.
* Fix chrome version typo and correct testing change that broke chrome UA chack
* simplity browser version detection by using maps instead of string splitting
* Add configuration to enable or disable choosing themes in Display Settings. Only for Licensed servers.
* Add configuration to enable or disable choosing custom themes in Display Settings. Only for Licensed servers.
* Add configuration to enable or disable a specific list of themes to choose in Display Settings. Only for Licensed servers.
* Added config value and logic for "DefaultTheme"
* Fix problem with undefined values when the server is not licensed
* PLT-7468 Moved more errors to use error types
* PLT-7468 Moved 404 error page to use error types
* Made helper function for rendering external links on error page
* Changed email batching short-circuit logic to look at last viewed at timestamp in channel member struct instead of in user's status struct, since the latter is only updated if the user's status is set to online
* Fixed unit tests
* Reduced right-hand drift
* Reduced total number of store calls by loading all channel member objects for user exactly once per team that the user received notifications for
* add S3 region to system console and add S3 validation
* update translation message
* add bool as return value to Validate* functions
* update Validate* functions to be pure
* PLT-7517 Added setting to enable tracing of Amazon S3 connections
* Removed unnecessary placeholders on boolean settings
* Added AmazonS3Trace to diagnostics
* Updated AmazonS3Trace setting name in system console
* Removing extra colon
* on "About Mattermost", add notes with links to notice.txt which has list of copyrights of open source components used
* remove apps from link
* Minor UI update
* Add config value EnableXToLeaveChannelsFromLHS that if true displays x to the right of private and public channels on the LHS.
* Displays x to the right of private and public channels on the LHS based on if EnableXToLeaveChannelsFromLHS=true.
* change the tooltip for private and public channels to `Leave channel`
* Add client-side event for when user clicks the "x" button. Different for public, private, DM.
