Started work on the stellar evolution table

The stellar evolution table, here abbreviated as StEvoTable, will con-
tain the entries of the table given in the rule book. The plan being
that several values can be referenced via an index.
Completed the stellar evolution table dict

Inserted the dict for the stellar evolution table (Space p. 103) that
can now be accessed globally.

The implementation of the usage of this table still has to happen in
the Star class.
Changes hard tabs to soft tabs

This commit changes all hard tabs to soft (space) tabs.
Add IndexTable

Add a new table called IndexTable. This table can be used to look up
the index for StEvoTable given two 3d roll results as described in
Space p. 101.
Outsource location of tables

The location of all GURPS tables is outsourced to GURPS_Tables.py from
where they can be imported to the other files where needed.
Merge branch 'master' into StEvoTable

I got fed up with not having the .gitignore file in this branch.
Implement usage of StEvoTable and IndexTable

Implement the usage of StEvoTable and IndexTable in the Star class.
This leads to significant enhancement of the readability of the code,
and hopefully leads to a greater ease of access to the contents of
StEvoTable.