Thread-safe and more performant parser based on ExprTK

[dilawar]

This PR replaces muParser by ExprTK based parser. The details are/will be in the code comments, the essentials are the following.

Parser related

• Replaced muParser with ExprTK parser.
• ExprTK is more performant than muParser (see benchmarks).
• ExprTK is thread-safe and the parser works great when both Ksolve and Gsolve are multi-threaded with some caveat ~(the PyRun expression must not update any moose.vec)~.
• Added a test based on Vinu's model. The values are almost equivalent to single-threaded version.
• The API remains the same. The expression format remains the same. Many more expressions are supported by ExprTK.

Other changes

• Removed outdated moose.Func. It has been replaced by moose.Function. (See #367 for Subha's comment)
• Ksolve and Gsolve can be turned into multithreaded by setting environment variable MOOSE_NUM_THREADS e.g. export MOOSE_NUM_THREADS=8 will make both Ksolve and Gsolve to use 8 threads. Alternatively use can set numThreads to 8.
• readSBML function has some cosmetic changes. I needed to print some values during the debug process.

Tests

• 9 more tests from rdesigneur scripts.
• 2 tests causes segfault at the end of simulation when memory is cleaned (related to #388). These tests are not run by default and have been moved to alpha directory.

Build system

• Added make docker which runs whole travis pipeline inside a docker image. If docker is setup, developers are encouraged to use make docker before pushing changes to repository.

TODO

• [x] memory leak. Fixed by https://github.com/BhallaLab/moose-core/pull/387/commits/51da6935f775a0d9d58b024ebab9dfe2ae24d96e

Before fix

==8883== HEAP SUMMARY:
==8883==     in use at exit: 168 bytes in 14 blocks
==8883==   total heap usage: 1,270,404 allocs, 1,270,390 frees, 254,115,799 bytes allocated
==8883==
==8883== LEAK SUMMARY:
==8883==    definitely lost: 152 bytes in 13 blocks
==8883==    indirectly lost: 0 bytes in 0 blocks
==8883==      possibly lost: 0 bytes in 0 blocks
==8883==    still reachable: 16 bytes in 1 blocks
==8883==         suppressed: 0 bytes in 0 blocks
==8883== Rerun with --leak-check=full to see details of leaked memory
==8883==
==8883== For counts of detected and suppressed errors, rerun with: -v
==8883== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

After fix https://github.com/BhallaLab/moose-core/pull/387/commits/51da6935f775a0d9d58b024ebab9dfe2ae24d96e

==23965== 
==23965== HEAP SUMMARY:
==23965==     in use at exit: 16 bytes in 1 blocks
==23965==   total heap usage: 1,265,916 allocs, 1,265,915 frees, 253,854,188 bytes allocated
==23965== 
==23965== LEAK SUMMARY:
==23965==    definitely lost: 0 bytes in 0 blocks
==23965==    indirectly lost: 0 bytes in 0 blocks
==23965==      possibly lost: 0 bytes in 0 blocks
==23965==    still reachable: 16 bytes in 1 blocks
==23965==         suppressed: 0 bytes in 0 blocks
==23965== Rerun with --leak-check=full to see details of leaked memory
==23965== 
==23965== For counts of detected and suppressed errors, rerun with: -v
==23965== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)