Add schema tables parse function

[oberstet]

we currently lack helpers like

• cfxdb/cfxdb/xbrnetwork/account.py

  Line 457 in c9717cd

  def parse(data):

for other classes. eg:

(cpy382_1) oberstet@intel-nuci7:~/scm/crossbario/xbr-www/cloud/planet_xbr_crossbarfx$ make import_db 
crossbarfx shell import database \
	/tmp/.xbrnetwork \
	/tmp/db.dat \
	--include-schemata xbr,xbrnetwork --exclude-tables xbr.blocks


Database table statistics [dbpath="/tmp/.xbrnetwork"]:

xbrnetwork.accounts....................: 20 records
xbrnetwork.idx_accounts_by_username....: 20 records
xbrnetwork.idx_accounts_by_email.......: 11 records
xbrnetwork.idx_accounts_by_wallet......: 14 records
xbrnetwork.verified_actions............: 63 records
xbrnetwork.user_keys...................: 42 records
xbrnetwork.idx_user_key_by_account.....: 42 records

Importing database [dbpath="/tmp/.xbrnetwork", filename="/tmp/db.dat", filesize=52426]:

Traceback (most recent call last):
  File "/home/oberstet/cpy382_1/bin/crossbarfx", line 11, in <module>
    load_entry_point('crossbarfx', 'console_scripts', 'crossbarfx')()
  File "/home/oberstet/scm/crossbario/crossbarfx/crossbarfx/__init__.py", line 221, in run
    sys.exit(main.run())
  File "/home/oberstet/scm/crossbario/crossbarfx/crossbarfx/shell/main.py", line 1412, in run
    cli()  # pylint: disable=E1120
  File "/home/oberstet/cpy382_1/lib/python3.8/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/home/oberstet/cpy382_1/lib/python3.8/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/home/oberstet/cpy382_1/lib/python3.8/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/oberstet/cpy382_1/lib/python3.8/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/oberstet/cpy382_1/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/oberstet/cpy382_1/lib/python3.8/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/home/oberstet/cpy382_1/lib/python3.8/site-packages/click/decorators.py", line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/oberstet/scm/crossbario/crossbarfx/crossbarfx/shell/main.py", line 426, in cmd_import_database
    exporter.import_database(filename,
  File "/home/oberstet/scm/crossbario/cfxdb/cfxdb/exporter.py", line 257, in import_database
    val = table.parse(val)
AttributeError: 'TokenApprovals' object has no attribute 'parse'
Makefile:146: recipe for target 'import_db' failed
make: *** [import_db] Error 1