Merge pull request #1715 from bergerjac/prs/GitHead

modified GitHead parse
Move CompositionContainer property to new GitUIPluginInterfaces.ManagedExtensibility class.
PluginRootIntroductionPage: remove "IsInstantSavePage: true"
SettingsPageBase: return also TextBox and ComboBox Text value to be found the the search
GitPlugin: save icons with 24bit
FormGoToCommit: fix help link and simplify label text
Move build server integration interfaces to GitUIPluginInterfaces.
FormChooseCommit: add button that opens the Go to commit dialog that helps to find a specific commit
Merge pull request #1721 from feinstaub/topic_pluginicons

GitPlugin: save icons with 24bit
Merge pull request #1718 from feinstaub/topic_fix_pluginintrosettingspage

PluginRootIntroductionPage: remove "IsInstantSavePage: true"
Merge pull request #1720 from feinstaub/topic_settingspage_search

Settings dialog: also find text from TextBoxes and Comboboxes
Merge pull request #1722 from feinstaub/topic_minor_gotocommitfix

FormGoToCommit: fix help link and simplify label text
Merge pull request #1723 from feinstaub/topic_gotocommit_in_choosecommitdlg

FormChooseCommit: add button that opens the Go to commit dialog that helps to find a specific commit
Merge remote-tracking branch 'gitextensions-pombeiro/BuildServerIntegration' into BuildServerIntegration
Merge remote-tracking branch 'gitextensions/master' into BuildServerIntegration
Fixed unstaging untracked files.
Prevent from nested call to Staged/UnstagedSelectionChanged.
Change code to retry reading from TeamCity REST interface when a login page is received.
Try to eliminate spurious credentials dialogs due to canceled tasks and login page responses.
Merge remote-tracking branch 'gitextensions/master' into BuildServerIntegration