Added autodetection and override of 32/64-bit mode
coremanager.py: Allow cores to reside anywhere in the cores tree

Thia removes the restriction that a directory containing a
.core file must have the same name as the .core file itself.
verilator: Clean up console output
Add a configure option to disable SVN-based providers

By passing --disable-svn, no SVN-based providers are installed.
This only affect the OpenCores provider at this point
coremanager.py: Fix ordering of dependencies
Allow dots in .core filenames
fusesoc.in: Remove redundant --systems-root argument
coremanager.py: Expand user names correctly
fusesoc.in: Warn instead of exit on missing cores_root
fusesoc.in: Add init command

The init command checks out the orpsoc-cores repo and writes a
default fusesoc.conf file if it doesn't exist
fusesoc.in: Add update command

The update command iterates through all detected cores_root, and
if it detects an upstream orpsoc-cores repo attempts to pull it
readme.md: Update installation instructions