Updated action functions and fixed a few bugs.

(1) Updated key mapping in DeleteLine() action function to correct
cursor selection bugs in certain custom edit controls.
(2) Created and updated code to support new RepeatLastCommand() action
function for repeating last user command in Command mode.
(3) Updated bug in window logic to use actual active window when Vime is
first activated, rather than the previously active window.
(4) Refactored status bar code into UpdateMetrics() to separate
function.
(5) Updated various files with typo/formatting corrections.