Added cms.runMigrationsOnLogin configuration item to control whether the UpdateManager automatically runs any pending migrations on login to the backend, various bug fixes

UX/UI Improvements

• The link to "Access Logs" in the System Dashboard Widget is now hidden when the user doesn't have access to view those logs.
• Reverted 457's improvements for screen reader accessibility and keyboard navigation in the backend as they are not production ready. Will be considered for inclusion in 459.
• Side panel header now styled with brand colors

API Changes

• Added cms.runMigrationsOnLogin configuration item to control whether the UpdateManager automatically runs any pending migrations on login to the backend. The default is now null which means that the value is pulled from app.debug; i.e. only enabled when the application is in debug mode.
• Field labels are now added as model validation attribute names after the field is checked for inclusion in the current context which solves an issue where multiple fields for the same attribute but under different contexts would conflict with each other.

Bug Fixes

• Fixed support for tab icons in the Theme customization form
• Fixed support for default values in nestedforms inside of repeaters in an update context
• Fixed bug where a CSRF token mismatch would display an error twice in the CMS section
• Removed support for the Priority Hints API in the {% framework %} tags as that broke existing themes that rely on a synchronous load order of the theme scripts
• Fixed minor issue where the editable part of the RichEditor FormWidget didn't fully fill the height of the control
• Fixed issue where calling isset() on CMS page codebase object properties wouldn't give the same result as actually accessing them.
• Fixed "widget not bound to controller" error for nested repeaters.
• Improved support for previewMode being passed down to Repeaters and NestedForms
• Fixed an issue where using unsupported database drivers would thrown an incorrect exception

Translation Improvements

• Added Thai translation

Community Improvements

• Added documentation for the DataTable FormWidget
• Added an issue template for marketplace issues