Small fixes

See merge request OPAL/src!441

Resolve "Opal-T fails to write LossDataSink if executed in parallel"

Closes #585

See merge request OPAL/src!439

Resolve "Compile error in unit tests"

Closes #600

See merge request OPAL/src!434

Resolve "Update Doxygen main page"

Closes #601

See merge request !435

Resolve "remove build of Doxygen LaTeX documentation"

Closes #597

See merge request OPAL/src!433

Resolve "Check that element length is long relative to a time step"

Closes #349

See merge request OPAL/src!430

check the length of the elements and compare it with the length of a time step; check that the user inputs for DT and MAXSTEPS of the TRACK command and for L of the elements are positive values; replace the length_m member variables in the elements with method call getElementLength;

Resolve "Compile error in unit tests"

See merge request OPAL/src!431

Resolve "ClosedOrbitFinder/SigmaGenerator: Charge not applied correctly"

See merge request OPAL/src!420

Resolve "compiler errors with AMR/SAAMG enabled"

Closes #587

See merge request OPAL/src!421

Resolve "replace all C assert with PAssert"

Closes #589

See merge request OPAL/src!419

Resolve "parse error in VFFA-1.in"

Closes #584

See merge request !418

Resolve "OrbitThreader doesn't track far enough when TRACKBACK=true"

Closes #586

See merge request OPAL/src!414

Resolve "compiler errors with clang9"

Closes #588

See merge request !416

Resolve "EBDUMP for 3DDynamic field maps not working if in subdirectory"

Closes #582

See merge request !411

Resolve "opal.el not working"

Closes #580

See merge request !410

Remove empty list and duplicated opal-font-lock-special_operators and opal-font-lock-special_constants

update opal.el for OPAL 2.4

See merge request !407