Altair RemoteStick Patch

This Patch handles all necessary changes to use the Altair Remote Stick
with the new XCSoar Versions.

Mainly:
     Key-Definitions have been made in order to use the Key-Events
(created by the RemoteStick) with the Event-Handler.
     Additional handling of Key-Events in the Quickmenu in order to
control the Menu by the RemoteStick (changing focus of button, "click"
on button, Escape-Function to leave the Menu again)
     Additional Keyevents in the Analyis-Page (to change the pages with
the RemoteStick and to leave the Menu)
po: update Dutch translation
Manual: Correct description of data file location on Unix/Linux

See trac issue #2729.
LogComputer: update comment
LogComputer: combine two GPSClock::SetDT() calls
NMEALogger: don't use BatchTextWriter

The standard TextWriter class does enough buffering, we don't need
another level of buffers.
po: update French translation
InfoBoxes/Time: add local NMEAInfo references
Formatter/LocalTimeFormatter: new library

Provides a wrapper for FormatSignedTimeHHMM(TimeLocal()).  Reduces
direct dependencies on LocalTime.cpp.
ComputerProfile: move code to LoadUTCOffset()

Don't override old value if the profile value is invalid.  Default to
the UTC offset given by the operating system.
TimeStatusPanel, WaypointInfoWidget: use ComputerSettings::utc_offset

.. instead of the glue function GetUTCOffset().
RoughTimeDelta: new class to wrap the configured UTC offset

Type safety.
LocalTimeFormatter: add utc_offset parameter
LocalTime: eliminate unused function GetUTCOffset()
TimeConfigPanel: use FormatLocalTimeHHMM()
CommandLine: add parameter "-datapath"

This Patch allows to specifiy the used DataPath for the XCS Data when
starting XCS with command line.
This will allow the direct use of the storage card in the Altair by XCS
(getting rid of the all omipresent storage problem in Altair), when the
AltairSync program will be updated by Triadis (otherwise the call is
still the same).
RoughTime: add operator+(RoughTimeDelta)
DataField/RoughTime: render values in local time zone

Implements TRAC ticket #2645.
LocalTime: move to src/Time/
AirspaceParser: use OperationEnvironment::SetErrorMessage()

Don't use MessageBoxX, remove UI dependency.