Avoid `set` and `get` prefixes for methods

[Tigrov]

Avoid set and get prefixes when declaring method names in the base ActiveRecord classes.

These prefixes will be used to access values of properties and relations e.g. getName(), setName()

Rename existing methods

• getTableName() -> tableName()
• getIsNewRecord() -> isNewRecord()
• getDirtyAttributes() -> dirtyAttributes()
• and so on

Also see

• #343