[#1654] Tweaking comments in channel handlers doc to point to reference
Update reference/constraints/Image.rst

Should be Image constraint
Update reference/constraints/Image.rst

Changes for the others also
Update flashbag syntax and add note on flash session lifetime
Minor terminology change
Add Brazilian Portuguese translation git repository
routing name updated according to new bundle generator and routing manipulation
Adding more detail to the DI compilation page
Updating to remove HTTPKernel specific method from di config processing examples
Adding a note that XSD validation of config files is optional
Changing syntax used for missing code sections
Fixing minor rst errors
Adding some information on adding links within the documentation
Adding another page to the console section with info on general usage
Adding info on running help without a specific command
Adding info on linking to the PHP documentation
Fixing errors in console usage article
add @WouterJ catches
Fix minor typo
Grammar correction in Performance section