Reorder and revamp the documentation

docs/sql_cheatsheet.md

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+# SQL Helper
+This page constains some help if you want to edit your sqlite db.
+
+## Install sqlite3
+**Ubuntu/Debian installation**
+```bash
+sudo apt-get install sqlite3
+```
+
+## Open the DB
+```bash
+sqlite3
+.open <filepath>
+```
+
+## Table structure
+
+### List tables
+```bash
+.tables
+```
+
+### Display table structure
+```bash
+.schema <table_name>
+```
+
+### Trade table structure
+```sql
+CREATE TABLE trades (
+	id INTEGER NOT NULL,
+	exchange VARCHAR NOT NULL,
+	pair VARCHAR NOT NULL,
+	is_open BOOLEAN NOT NULL,
+	fee FLOAT NOT NULL,
+	open_rate FLOAT,
+	close_rate FLOAT,
+	close_profit FLOAT,
+	stake_amount FLOAT NOT NULL,
+	amount FLOAT,
+	open_date DATETIME NOT NULL,
+	close_date DATETIME,
+	open_order_id VARCHAR,
+	PRIMARY KEY (id),
+	CHECK (is_open IN (0, 1))
+);
+```
+
+## Get all trades in the table
+
+```sql
+SELECT * FROM trades;
+```
+
+## Fix trade still open after a /forcesell
+
+```sql
+UPDATE trades
+SET is_open=0, close_date=<close_date>, close_rate=<close_rate>, close_profit=close_rate/open_rate  
+WHERE id=<trade_ID_to_update>;
+```
+
+**Example:**
+```sql
+UPDATE trades
+SET is_open=0, close_date='2017-12-20 03:08:45.103418', close_rate=0.19638016, close_profit=0.0496  
+WHERE id=31;
+```
+
+
+## Fix wrong fees in the table
+If your DB was created before 
+[PR#200](https://github.com/gcarq/freqtrade/pull/200) was merged
+(before 12/23/17).
+
+```sql
+UPDATE trades SET fee=0.0025 WHERE fee=0.005;
+```