Update folders structure

[victorapm]

Consider a new organization structure:

├── data
├── src
    ├── solver
    ├── precon
    ├── linsys
    ├── misc
├── include
├── examples
    ├── amg
    ├── mgr
     ...
└── test
    ├── system

The folders:

1. examples: quick-start examples for users
2. data: some example matrices/vectors
3. test/system: test whole system (end-to-end) application