Update Scenario Cheatsheet to mention MVEL and Background

Update Scenario Cheatsheet for MVEL expression usage.

Here are some topics that could be mentioned:

Expressions for Rule based scenarios for simple types

• Starts from "#"
• Runs for properties
• Runs for duplicated properties
• Returns the same type as property type in GIVEN
• Returns boolean in EXPECTED
• Receives rule processed value as a parameter in EXPECTED via keyword "actualValue"
• Applies java.util.Objects.equals(actualValue, expression result) on the expression result if the EXPECTED value not a boolean
• Could run any of java function for the project
• Exports and imports as any other value

Limitations
1. Mvel expression results not property same type - drives scenario failure, error reason and highlighted
Use case:
User inputs 1/2 to Integer property
2.Mvel execution throws exception - drives scenario execution stopping, failure, error alert
Use case:
User inputs inexistent MVEL function in one of the properties
3.Mvel expression exception stops expression execution for all EXPECT colons
Use case:
User got one of the GIVEN fact expression excepted
4.Mvel cannot be mixed with simple expressions in one cell
Use case:
For cell inputs :

[#4+4,68]
#actualvalue>1