New operations for table.py

[yizerozhuang]

1. In friesian/table.py, update function "to_list" which is able to contains mutiple column.
2. In friesian/table.py, add function "iloc" which is able to change the value of a cell given column and indexes.
3. In friesian/table.py, add function "sort" which is able to sort the dataframe with given columns and orders.
4. In friesian/table.py, add function "append_list" which is able to append the table with given value and indexes.
5. In friesian/table.py, add function "shift" which is able to shift column with given value and indexes.
6. Write corresponding testing in test_table.py.

[hkvision]

iloc and append_list may be hard to work for big data, pending on this. Let's put shift in a new PR and merge it first. cc @jason-dai