first commit on rewrite
add set_autocommit for database
add transcation
rm close_cursor; add transaction; stop patching cursors
add sql;expr
indentifies to sql
add model; add runtime
tests for Model
add runtimes2sql
add CURD queries
add some classmethods for Model
add r** operators
add custom operator; add sql2sql; add op_str to Expr
add __all__ to module
Merge branch 'rewrite' into issue22

* rewrite:
  add __all__ to module
  add custom operator; add sql2sql; add op_str to Expr
  add r** operators
  add some classmethods for Model
  add CURD queries
  add runtimes2sql
  tests for Model
  add model; add runtime
  indentifies to sql
  add sql;expr
  rm close_cursor; add transaction; stop patching cursors
  add transcation
  add set_autocommit for database
  first commit on rewrite