Define coding style guidelines

**User Story**
As a `contributor` I want `coding style guidelines` so that `our code becomes more readable through consistent formatting and practices`.

**Impacts**
- [x] Other (please add below)
Code quality

**Additional Context (optional)**
https://isocpp.org/wiki/faq/coding-standards

## CORE TEAM TASK LIST
- [ ] Consensus regarding formatting rules
- [ ] Formatting
- [x] Maximum line length: 118
- [x] EOF: 1 newline
- [x] Code block separation: 1 newline
- [x] Long calls: Use [496c622](https://github.com/bitshares/bitshares-core/commit/496c6229e13bd511c2380f9c8d540e68bd65a65d)
- [ ] Spaces: In discussion. See [Wiki]()
- [ ] Comments
- [ ] In-line
- [ ] In code blocks
- [ ] In test cases
- [ ] Naming
- [x] Methods: all lowercase with "_" as word separator
- [ ] Other?
- [ ] Scoping
- [ ] In lambda:
- [ ] In large refactor:
- [ ] Avoid global variables
- [ ] Classes
- [ ] Please add
- [ ] Functions
- [ ] Please add
- [ ] Exception Rules
- [ ] Please add
- [x] Architecture
- [x] Create/modify/delete of the database inside operation evaluator must be done in `do_apply` and **never** in `do_evaluate`
- [x] Bump database: when new fields are added or removed to objects
- [x] DATABASE_VERSION format: YYYYMMDD
- [x] PR against:
- [x] `develop` if no impact to consensus logic
- [x] `hardfork` if consensus impacting
- [ ] Identify a tool(s) that can do it automatically
- [ ] Perform whitespace-only change

Start with the issue checklist, the linked C++ coding-standards FAQ, and commit 496c622. Resolve the outstanding formatting, comments, naming, scoping, class, function, exception, and tooling questions with the core team. Done means agreed coding guidelines, an identified automatic formatting tool, and the requested whitespace-only change.

Written by the indexing model from the issue text.