rough implementation of btree in memory
Separated operations with binary data in order to reuse code in indexes
1. Moved record's set and getString to PageData
2. Moved PageData out of class Page
3. Renamed PageData to DataHolder
btree on pages
put and get with tuples seem to be ok
Creating and loading indexes
Basic where clauses parsing.
Columns validation refactoring
Small Table refactoring
Added assert that columns are unique on table creation
Test: create table with duplicate columns
Test: insert with duplicate columns
Test: select all (currently does not work)
Added matcher sketch
Index matching sketch
Merge remote-tracking branch 'origin/where' into indexes

Conflicts:
	src/main/java/ru/spbau/mit/dbmsau/table/RecordSet.java
'select * from test where id = 3;' works
Rename columnNumber -> columnIndex
Currently not used
Refactoring: split table into table and relation
Global code reformat
ColumnAccessors. 'Select test.name, id from test;' works
Another global reformat by idea