CMS-4182 TreeGrid - Automatic loading of remaining children

Renamed generic type NODE to DATA in the `TreeGrid` and `TreeNode`.
CMS-4135 ContentService.create should create a valid name from displayName if not given
Merge pull request #963 from enonic/CMS-4135

CMS-4135 ContentService.create should create a valid name from displayNa...
Added source generation to project.
Added source generation to project.
CMS-4135 ContentService.create should create a valid name from displayName if not given - tests.
CMS-4169 Remove Site Template - Support PageTemplate being a Content
PageTemplate is now a Content which to be created below a Folder named "templates" under a Site
A PageTemplate is now renderable
Refactored Site to extend Content instead of being a property of Content
Removed SiteTemplate (TODO: Remove remaining SiteTemplate classes and Template App in UI?)
Merge pull request #964 from enonic/CMS-4135

CMS-4135 ContentService.create should create a valid name from displayNa...
CMS-4169 Remove Site Template - Support PageTemplate being a Content
Removed SiteTemplateWizardStepForm
Added ModuleKey.from(Class) for getting the module key from loaded class.
CMS-3888 Streamline module development
Supported usage of ModuleKey.from(Class)
CMS-4203 Remove Site Template - Make proper commands for all methods in PageTemplateServiceImpl
CMS-4172 Introduce data for Metadata on Content
CMS-3888 Streamline module development
Removed SiteService and SiteResource, since all methods except getNearestSite was no longer in use
Moved getNearestSite to ContentService
Merge remote-tracking branch 'origin/master' into CMS-4203
Merge pull request #967 from enonic/CMS-4172

CMS-4172 Introduce data for Metadata on Content
Merge remote-tracking branch 'origin/master' into CMS-4203
Merge pull request #968 from enonic/CMS-4203

CMS-4203 - Remove Site Template - Make proper commands for all methods in PageTemplateServiceImpl
Fixed bug in GetNearestSiteRequest
Fixed clean grunt task