Add "simple" mode with common parameters

[tomasr78]

Add "simple" mode with common parameters to let user easily make conversions without digging deep into specification.

Example conversion one file to one file. DOCX->PDF

convertapi.exe c:\fileToConvert.docx c:\fileToSave.pdf -- secret <your secret>

One file to many files. ZIP->EXTRACT

convertapi.exe c:\fileToConvert.zip c:\folderToSave -- secret <your secret>

Also --params parameter can be accepted to allow additional parameters to be set.

[tomasr78]

Implement this too and add this to GitHub documentation