Switch caching implementation

[ctmay4]

The library is currently using Caffeine. That library still uses sun.misc.Unsafe. There is an issue to look into it (ben-manes/caffeine#273), but there has been no movement.

This merge request switches the caching library to Cache2k which has no deprecated dependencies and it fully compatible with Java 9+.

[ctmay4]

The new library is working well. The performance in heavily threaded workflows is improved as well.

Caffeine

Starting schema selection tests from cs_schema_identification.txt.gz [7 threads]
Completed 8,908,918 cases in 19.59 s (0.002ms/case).
Starting carcinoid_appendix.gz [7 threads]
Completed 2,565,807 cases for carcinoid_appendix.gz in 1.404 min (0.033ms/case).

Cache2k

Starting schema selection tests from cs_schema_identification.txt.gz [7 threads]
Completed 8,908,918 cases in 15.02 s (0.002ms/case).
Starting carcinoid_appendix.gz [7 threads]
Completed 2,565,807 cases for carcinoid_appendix.gz in 1.345 min (0.031ms/case).