[gnulib-tool-py] GLModule improvement

[address@hidden]

Hello everyone!

Today I've got a new idea how we could improve this module. We can add 
file-like interface to it by implementing new attributes.

path: the same as before.
mode: can be 'r' or 'w', where the first means that we read existing file, the 
second means that we write (i.e. create) new file.

For read mode there are only get* methods available. For write mode there are 
all methods available.

That means that developers can check whether module exists using 
GandLModuleSystem, and if not, create it from zero using couple of set* 
methods, then using addFiles method to add .c and .h files and then applying 
save method. That will take approximately hour to change GLModule, so I'd like 
to do it today if you think that it is a good idea.

So what do you think?