Uniswap modifications to enable summarization

[mariaKt]

This PR creates a copy of the UniswapV2Swap test, and makes the following changes, mostly related to names:

• replace all names starting with a capital letter. We replace the capital letter with the lowercase letter, or append a descriptive prefix. This is done to avoid having these names treated as Variables from the K parser when parsing a configuration.
• replace names that include underscores. We convert the names to camel case. If the names start with underscore, we also append a prefix (vid for variables, fid for functions).
• we add names to key and value types of mappings. This is done because accessors automatically generated by the semantics are prefixed with $, and the parser attempts to treat them as symbolic variables.

The test has been locally tested to rewrite to .K for the provided input.

[mariaKt]

I set up the infrastructure for testing in the examples directory. The idea is that we may want to execute a contract with multiple .tnx files , or none. So, I chose the convention that the transactions will have the same directory structure as the examples directory, but for each C.sol file there will be a matching directory, named C. C will contain all transaction files .tnx we want to execute C.sol with. For each T.tnx, C will also contain the corresponding reference output T.ref.