* Add exchange manager to engine
* Several improvements for engine and friends
1) New file.Exists func
2) gRPC TLS cert expiration date check and regeneration
3) New donation var for use across the codebase
4) Use Go log package until the logger is initialised
* Add cert tests and create dir tree if it doesn't exist for file.Write
* Link up donation address to documentation tool plus minor adjustments
* Fix remaining donation addrs
* Move non-needed reload exchange funcs
* Revert accidental config_example.json changes 🕯️
* Use go logger for logging until the logger has initiliased, otherwise no output will be seen
* Link up portfolio delay val and other fixes
* Run go mod tidy after dependabot PR
* Address nitterinos
* started adding basic lru cache system
* Added basic LRU cache including Add Get Remove Contains ContainsOrAdd Clear
* wording changes on comments
* removed exported var's in strut as they are not required
* Added README
* README updates
* rm line :D
* swapped to mutex over rwmutex updated comments
* unexported getNewest & getOldest
* unexported getNewest & getOldest
* Updated comments and cited references in source
* updated comments
