Coap 18

Based on the 2 commits from pull request #507 i used Uncrustify and fixed Travis build errors.
Also added function for easy block1 usage and fixed blocksize calculation when REST_MAX_CHUNK_SIZE != 2^x. Added an example for block1 + separate + block2.

Wasn't sure how to publish it, because pull request #507 was never merged. Maybe i need to make a pull request to mkovatsc/contiki first?