Update docs

[retgits]

Fixes: .

What kind of change does this PR introduce? (check one with "x")

[] Bugfix
[] Feature
[] Code style update (formatting, local variables)
[] Refactoring (no functional changes, no api changes)
[X] Other... Please describe: Updating the readme files of the activities

What is the current behavior? Readme files are inconsistent and sometimes incorrect

What is the new behavior? We now have consistent and correct readme files for the activities

[mellistibco]

we should also update the mapping types for the samples to use the new string literal value vs the number value.

assign | Direct mapping. Assigning the value from var1 to var2. No other implied logic.
literal | A literal mapping. For example, mapping the string “hello” to a string typed variable.
expression | Expression mapping. This enable using functions and expression condition in mamping
object | Complex object. Used when a JSON-based complex object must be built and assigned.
array | Array mapping. Mapping an Array of Objects.