This introduces two new source files, keystore.cpp and wallet.cpp with
corresponding headers. Code is moved from main and db, in a preparation
for a follow-up commit which introduces the classes CWallet and CKeyStore.
there is no internal modification of any file in this commit
files are moved into directories according to established standards in
sourcecode distribution; these directories contain:
src - Files that are used in constructing the executable binaries,
but are not installed.
doc - Files in HTML and text format that document usage, quirks of
the implementation, and contributor checklists.
locale - Files that contain human language translation of strings
used in the program
contrib - Files contributed from distributions or other third party
implementing scripts and auxiliary programs
