Drop unused skip_abs option for Expr.compute_leading_term and calculate_series

    This was introduced in 89c7626 and then this option was unused since 9c46974
Drop obsoleted docs about skip_log option of compute_leading_term()

    This was replaced by logx option in 9c46974d
Add logx option for lseries()
Drop _eval_lseries from exponential.py
Rewrite calculate_series with lseries
Explicitly specify Order variables in various series methods
Remove unneeded substitution of log(w)
Merge branch 'master' into logx-for-lseries
Simplify calculate_series() output with cancel(), not factor_terms()
Merge branch 'master' into logx-for-lseries

Conflicts:
	sympy/core/expr.py
	sympy/integrals/integrals.py
	sympy/series/gruntz.py
Merge branch 'master' into logx-for-lseries
Merge branch 'master' into logx-for-lseries
Merge branch 'master' into logx-for-lseries
Add logx options after new merges
Explicitly call lseries, not series with n=None
Merge pull request #2446 from skirpichev/logx-for-lseries

Add logx support for lseries