Cleanup Mul._eval_is_imaginary
if x and y are real, x**y is real indeed and real and imaginary parts
do not need any further expansion.
Fix 188fce4: Pow.is_real is True if base>=0 and exp>=0
Fix cse-related failure in test_issue_3022
Move new Pow.is_real tests to the right place
Modified printers, added dyadic back
Corrected all tests and ensured running
Tests run okay, mechanics core modified to depend on physics.vector
Interactive printing imports from mechanics
Added module to setup file
Modified arg test for CoordinateSym
Removed private functs from namespace, moved dynamicsymbols
Fix mpmath index files
Add dispersion examples to docstrings
Add OO interface in polys for the computation of the dispersion
Document OO interface to dispersion
Merge pull request #2786 from skirpichev/gh2785

solve_univariate_inequality shouldn't assume solve output is sorted
added documentation for discrete RV types
solve_univariate_inequality: don't assume that solve returns real solutions

    closes #2794
Docstring fixes in sympy.tensor.tensor

Added new example about symbolic data inside a tensor.