XML Console: Make account selectable
The XML Console being account-specific has one drawback: It cannot capture stanzas without an account (e.g. IBR stanzas while creating an account).
This adds an account selector to the filters window where all accounts are listed. Additionally, 'All accounts' (default setting) is selectable, which will display all stanzas. The console will print the stanza's account as well. With this change and the XML Console not being account-specific anymore, I hereby propose to move it into Gajim's 'View' menu, where it can also have a hotkey (Ctrl+Shift+X).
I also changed the action button order, replaced one icon (Clear) and replaced the Send button by one with a mnemonic. The console's Enable switch in the titlebar war removed as it did not serve a meaningful purpose here.