Implement the ability to customise shell arguments via dconf.

Added a shell-args key to implement the functionality outlined in
p-e-w/finalterm#100. To make your shell a login shell, simply set the
value of aforementioned key to the following:

    ['-l']
Update about dialog credits; small code layout adjustment
Fix #71

The problem was a strange condition where the layout manager
sometimes first allocates a large space (say, 20 x 20 characters in size)
for the line container, which triggers a (delayed) resize cycle,
and then immediately afterwards allocates a smaller, often invalid
(20 x 0) space, aborting a legitimate resize.
Fix #38

Some platforms having outdated versions of Clutter or its Vala bindings
cannot compile Actor.x_expand; this has therefore been replaced by
a workaround due to Tom Beckmann.
Added ```ls``` option to directory menu. (Fix #109)
Support command line options.
Use vapi for Config namespace.
CMake: configure_file use @ONLY

Don't replace ${foobar} strings which are valid expressions in some shell
files. Only replace @foobar@ occurrences.
CMake: Don't generate C files each time (touch them).
Merge branch 'configvapi' of https://github.com/Lasall/finalterm
Merge branch 'configurefileonly' of https://github.com/Lasall/finalterm

Conflicts:
	CMakeLists.txt
Merge branch 'cmakegenc' of https://github.com/Lasall/finalterm
Minor style adjustments
Update README to reflect changes to http://finalterm.org
Create gnulib project for OS X compatibility.
Ignore all the generated files in gnulib directory.
Add gnulib as an autotools external project.
Actually copy the header file.