Cleanup of ButtonsPanel
Removed unneeded instances of the this keyword.
Added a description of the class.
Disables the vote on session button when in the voting panel
Added documentation and refactored the toolbar button enabling and disabling in the OverviewTreePanel
Fixes minor end voting button issues
Merge pull request #140 from TheTeam8s/enhancement-disableVoteButton

Disable the vote on session button when the voting tab is open