Reworked the PasswordGeneratorWidget.

It's loosely based on OS X PasswordAssistant. Generation happens as soon as a
change is made, and on open of the widget. A combobox has been added to allow
one to choose from some randomally-generated alternatives, and the UI is
generally been made a bit more compact.

Written by Michael Curtis <michael@moltenmercury.org> and revised by me.

Closes #119

https://github.com/keepassx/keepassx/pull/38
Move password generator widget to the right row.
Uncheck the correct widget in ChangeMasterKeyWidget.

We want to enable the password group but mask the password in the line edit.
Use monospace font in the password generator combo box.
Drop superfluous PasswordGeneratorWidget::togglePassword slot.
Drop new database action from the toolbar.

It's not a common operation.
Add copy username and password actions to the clipboard.

Also add corresponding icons that I've put together from
various Oxygen icons.
Add 22x22 icons for actions that are in the toolbar.
Coding style fixes.
Replace ArgumentParser with a backport of QCommandLineParser from Qt 5.2.
Fix include guards of config-keepassx.h.
Set the application name and version in QApplication.
Small optimization in SymmetricCipherGcrypt::processInPlace().
Add KeePass 2 document icons.
Install mime info package on Linux.