Cleanup tools folder

There where files that were broken for at least 15 years.
It is better to no tools, then broken tools.
Grids can be generated with hypnotoad, for example, which
is actively maintained.

Author: dschwoerer

tools/README.md

@@ -2,19 +2,5 @@ pylib
 --
 Library of Python tools. This is the mainly used interface for post-processing.
 
-idllib
---
-Library of IDL tools
-
-matlablib
---
-Library of Matlab tools.
-
-eigensolver
---
-Eigenvalue solver for ITG test case
-
-pdb2idl
---
-Library for reading PDB files into IDL
-
+Other tools where removed with v5.3.0, as they where unmaintained.
+You can find them in older versions, e.g. in [5.2.0](https://github.com/boutproject/BOUT-dev/releases/tag/v5.2.0)