candidate fix for get_motion_params() bug

- Change integration style.
- Update tests to accomodate integration style change.
- doc revision for get_motion_params()
Generalize the code printing of And, Or, Not.

Move the printing of And, Or, and Not up in the class hierarchy to
the CodePrinter class and make it customizable by overriding a dict.
Add Fortran code printing for And, Or, Not, add tests.
Generalize the code printing of Relational.

Allow relational operators to be overriden using a dict.
Fix the Fortran printing of Ne, add tests.
Implement Fortran printing of Xor, Equivalent, add tests.
Fix the precedence order for Relational.

Relationals are somewhere between And and Add operations
in the precedence tables for python, C, Fortran, etc.
Split gmpy & matplotlib tests again (to 3 splits)
Add test for bug in piecewise integration

*  Integral(exp(x*t),(t,0,y)).doit() fails
Fix bug in Piecewise._eval_interval

- now has a consistent return form
Remove the spaces from the definitions of operators.

Instead, the spacing is done directly by the _print_Op methods.
Merge pull request #2545 from zanzibar7/get_motion_params_bugfix

candidate fix to get_motion_params() for issue #2543

close #2543
Merge pull request #2555 from skirpichev/travis-3

Split gmpy & matplotlib tests again (to 3 splits)
Merge pull request #2556 from jrioux/printing

Fortran code printing of logical and relational operators.
Merge pull request #2557 from zanzibar7/bug_piecewise

Bug piecewise