Pyheadtail

Typo fixed in transverse_spacecharge.py -- thanks to Cedric Hernalsteens for spotting!

**Hotfix:** Transverse Space Charge bug fix

transverse_spacecharge.py (based on PyPIC v2.0.0) used the
horizontal beam field in the vertical kick, typo is now fixed.
Transverse_Efield_map.py had it correctly.

**Hotfix:** Linear longitudinal tracking accepts Qs in the form of a 1D array with length of one, as provided by the PyHEADTAIL synchrotron.

**Hotfix:** indentation typo in transverse tracker

Transverse_Efield_map and RFBucket changes

Transverse_Efield_map changed `__init__` argument interface
which takes a general Slicer instance instead of fixed slicer
initialisation arguments.

Also much improved determination of Hamiltonian value
determination for RFBucket in case of phi_offset and multi-harmonics.

Hotfix: particles.p0 has been calculated slightly wrong.

Thanks to Mauro Migliorati for noticing the bug which
effectively lead to about 7% too large momentum increase
during acceleration (per turn). The problem was the formula
to calculate the gamma when changing p0 -- it involved
beta (but didn't re-calculate it, instead it took the one
from before). Now it is self-consistent and correct.