[Core] Shared assets project fixes

Syncronize referencing projects when files are added/removed/modified.
Set the project id when creating a shared project
[NuGet] Remove backslash from addin.xml
[NuGet] Improve check box spacing in package source preferences.

Make the spacing the same on each side of the check box. Previously the
checkbox was closer to the left hand side.

Move check box up slightly.
Shared Assents Projects fixes

Don't show the "project won't be built" message if the project doesn't
support building.
Also fixed NRE.
[Icons] [MonoDevelop.PackageManagement] Fixing some positioning issues
[MonoDevelop.Ide] Minor visual beautification of the toolbar status area
[Icons] More icon alignment fixes
[Ide] Switched default pad font to lucida grande 11 on mac.
[NuGet] Small adjustments to package source preferences UI.

Move text down 3 pixels.
Move checkbox down 5 pixels.
Move everything to the right 2 pixels. Uses a dummy column to get a
slightly more even spacing around the checkbox.
Merge pull request #517 from crdeutsch/patch-1

Change Update Check to Every 1 Days
Merge branch 'retina-package-source-preferences' into retina
[NuGet] Fix updated packages being added to recent package list.

Only add packages that the user installed from the Add Packages dialog
to the recent package list.
Track api changes
Save/Load the default namespace of shared projects
[C#] Shared file fixes

Properly update the project context in the path bar when files are added or
removed from projects.
[Ide] Fix project reloading issue

When checking if a project needs to be reloaded, check all files of the
project, not only the main file.
Fix version control issue with shared projects

When adding a shared project to a solution, make sure both the shproj and
the projitems files are added to the version control system.
Also fixed a NRE.
Renamed CanRunTarget to SupportsTarget
Solution configuration fixup

Don't create build configurations for projects that don't support building.
Fix NRE

It happens when the current loaded solution doesn't have any configuration