GUI for CSV import

This patch implements GUI for importing CSV log files. One is able to
configure what columns contain time, depth and temperature fields.
Pre-configured log applications currently included are ADP log viewer
and XP5. (Both of these use actually tab as separator, so the field
separator currently hard-coded.)

[Dirk Hohndel: minor fixes]

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Helpers: move some date related function to qt-gui.cpp

divelist.c:
get_dive_date_string()
get_short_dive_date_string()
get_trip_date_string()

MinGW support for *printf and parameter positions (e.g. %1$d)
is horribly broken. Instead of implementing *proper* support
for this feature Microsoft decide to ignore the standard (again)
and they implement new functions with the '_p' suffix,
such as 'sprintf_p', which seem to be available from a 2003 runtime.
To top that 'sprintf_p' is not really a 'sprintf' but rather
a 'snprintf'.

It seems that the MinGW people ignore the issue and do not provide
wrappers of any sort, or at least for the current recommended compiler
for Qt 4.8.5 on Windows - which is a 4.4.0. A note of warning;
inspecting how MinGW does certain things in headers such as stdio.h,
can ensue bad dreams or other negative effects on to the viewer.

This forces us to move the following functions from the 'back-end'
(divelist.c) to the 'front-end' (qt-gui.cpp) and use QString.

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>