ToolTabs.cs: fix 2 issue:
1) fix issue reported by mr. Skasi in #85 ("duplicate channel name with capital letter confuse ZKL"). Cause of bug: "Collection" item in NET uses case-insensitive string as key. Manual search fix this.
2) possible fix to issue reported by mr. Licho ("Chat Control not really closed when its told to close, results in error in log"). Cause of bug: wrong assumption that "panel.Controls" is indexed by string, result in incomplete item removal.

fix https://github.com/ZeroK-RTS/Zero-K-Infrastructure/issues/85
Merge pull request #235 from xponen/zkl_issue85andChannelCloseButNot

ZKL: fix channel case-insensitiveness & possibly fix channel not really close when closed