Consistently name README files and clean up

[tautschnig]

Please review commit-by-commit (the first one just changes file names).

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• n/a Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[TGWDB]

Nice tidying up

[codecov]

Codecov Report

Base: 78.34% // Head: 78.34% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (107ff85) compared to base (a53fa0f).
Patch coverage: 92.63% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7347   +/-   ##
========================================
  Coverage    78.34%   78.34%           
========================================
  Files         1644     1645    +1     
  Lines       190313   190358   +45     
========================================
+ Hits        149097   149133   +36     
- Misses       41216    41225    +9     

Impacted Files	Coverage Δ
jbmc/src/janalyzer/janalyzer_parse_options.cpp	48.58% <ø> (ø)
.../src/java_bytecode/character_refine_preprocess.cpp	54.27% <ø> (ø)
...mc/src/java_bytecode/character_refine_preprocess.h	100.00% <ø> (ø)
jbmc/src/java_bytecode/ci_lazy_methods.h	100.00% <ø> (ø)
jbmc/src/java_bytecode/ci_lazy_methods_needed.cpp	98.41% <ø> (ø)
jbmc/src/java_bytecode/ci_lazy_methods_needed.h	100.00% <ø> (ø)
jbmc/src/java_bytecode/code_with_references.cpp	84.61% <ø> (ø)
jbmc/src/java_bytecode/java_bmc_util.cpp	100.00% <ø> (ø)
...mc/src/java_bytecode/java_bytecode_convert_class.h	0.00% <ø> (ø)
...src/java_bytecode/java_bytecode_convert_method.cpp	97.69% <ø> (ø)
... and 409 more

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[jimgrundy]

Nice cleanup.