Add support for specifying additional JVM arguments

[ShadelessFox]

This pull request adds a new launcher argument, --launcher.additionalVmargs, that is supposed to be followed by a list of locations of files containing extra JVM arguments. Locations can potentially contain environment-variable strings in the form of %VariableName% regardless of the platform:

--launcher.additionalVmargs
%XDG_DATA_HOME%/DBeaverData/settings/dbeaver.vmargs
%HOME%/.local/share/DBeaverData/settings/dbeaver.vmargs

The launcher will attempt to read a file for every location in the declaration order until it succeeds. JVM arguments specified in such a file have higher priority than the ones defined in the launcher arguments or the configuration file.

A file containing extra JVM arguments follows the same structure as any other configuration file: every new argument is placed on its own line:

-Xms64M
-Xmx128M

The argument is intended to be used by developers of Eclipse RCP applications. It can be defined as <programArgs> in the .product file to allow end-users to specify JVM arguments if they can't do that otherwise by modifying the configuration file.

Additionally, 7e684f2 brings configuration file resolution for the console launcher with the -cli postfix in addition to the existing c postfix on Windows.