Merge pull request #83 from dgelfand/master

A running version with all changes by Andreas and Daniil included.
Move code of file tab into separate class FileTab.
Add menu item to split panel horizontally or vertically.
Start from single panel in the main window and split it on demand.
Fix splitting of left component.
Close panel
Create common superclass AnimationPanel for graphics panels.
Unregister panels from SimulationAnimation upon closing.
Set particle panel as default panel when splitting panels.
Show "close panel" menu item only for components in JSplitPane.
Replace panel also at top level.
Clean up code, extract method.
Merge pull request #84 from aipp/graphicspanel

Split panels horizontally or vertically
Bugfix: use correct types in YAML parser.

Now "gridStep: 0.5" is allowed in the YAML input file.
Merge pull request #85 from aipp/bugfix

Bugfix: use correct types in YAML parser.
Add output files to YAML Settings file.

- add a path. Output files are created in 'output'/path/...
- read spectrumstep from the YAML file.
Merge pull request #86 from dgelfand/master

Now the normalization of currents should be correct.
Move readFile() and writeFile() to new class FileIO.
Read input through YAML file also in batch version.

(also remove unused lines of code)
Initial conditions for Weibel instability added.