Thunderbird:UI Reduction

There's too much of it. It needs consolidation and simplification. It also needs reorganization.

For example, the Options Dialogue is poorly organized right now.

• The Options Dialogue is accessed by the Preferences menuitem (this is inconsistent, is there a bug on it?).
• Fonts and Display should be merged under Mail Display.
• Some of the options are used by very few users and should be ditched in favour of system default.
• The junk mail dialogue should be merged into options and grouped along with sanitization options, password options, certificates etc. under Junk Mail and Privacy (bug 257990).
• Return Receipts Options should be placed under Composition and Connection Settings should be placed under General (just like firefox).

The Account Settings also needs a redesign.

• We should design something similar to firefox's Bookmark Manager with account grouped by their types (Email, Newsgroup and RSS) on the left pane and the specific settings on the right pane. By default, we will only have one pane with server settings, logins settings, folder settings (user local folder or individual folder), certificate settings and composition settings (html or plain text)
• Moving the Account Settings into the Options dialogue is being investigated in bug 286664.