Possibility to add line termination character on file save

[FilipVanVooren]

Although DV80 records by itself do not require any line termination characters, some basic dialects (e.g. RXB) and tools expect a line termination character when reading basic source code from a DV80 file.

1. Introduce the possibility to add a line termination character upon saving a DV80 file.
2. Toggle F6 in dialog save, save block, print block will turn line termination on/off.
3. Option dialog for specifying line termination character(s)

There should also be a possibility to (automatically) strip away these pesky line termination characters when reading a DV80 file.
That will be handled via a separate issue.

[FilipVanVooren]

MVP implemented in Stevie 1.5.2
Option to specify line termination character will be added at a later time (and via separate issue)