Added new difficulty options for gameplay

The storyline and endless modes support 3 difficulty settings, each one with its own difficulty modifiers:

• casual: low matching threshold, less cash from orders, 2 credit insurances [ENDLESS], lvl1 tools (power inspector and components inspector)
  
• normal: medium matching threshold, more cash from orders, 1 credit insurance [ENDLESS], lvl1 power inspector
  
• hard: high matching threshold, great cash from orders, no credit insurance [ENDLESS], no tools
  

Added brand new tools

Added new helper mechanics (tools) which can make Ilie's life easier when building new PCs:

• Power inspector tool, inspects power consumption so you may never deliver a PC that never starts. Can be upgraded to work faster.
  
• Components inspector tool, inspects if the necessary components for the order are on the table. Can be upgraded to work faster.
  

Added a new "lifesaver" mechanic (ENDLESS mode only)

Ilie can buy credit insurance for the rainy days. When he is unable to pay the debt to the bank on that day, the credit insurance will save him.

Other bug fixing and gameplay improvements.