Release v2.0.0-dev6

Changes in v2.0.0-dev6 (since v2.0.0-dev5):

Edwin Eefting (16):
      created script to assist in creating releases
      bug fix: plugin_id should not start with a 0. (compiler interprets this as octal!)
      Revert "bug fix: plugin_id should not start with a 0. (compiler interprets this as octal!)"
      bug fix: plugin_id should not start with a 0. (compiler interprets this as octal!)
      added NDIR CO2 Sensor MH-Z19 plugin to TESTING plugin set
      remove artificial sensor startup delays. (now all sensors are send immediatly after booting and wifi-connecting)
      do hardwareinit() earlier so that outputs are set immeadiatly instead of waiting for connect. fixes https://github.com/letscontrolit/ESPEasy/issues/114
      enable status light as soon as wifi is connected
      use sizeof instead of magic numbers
      Implemented speaker and tone functions from https://www.letscontrolit.com/forum/viewtopic.php?f=4&t=343&hilit=speaker&start=10
      enabled Arduino OTA for dev-firmware only, to ease developing. minor output-tweaks
      cold boot startup delay
      major change: changed the timing of the first sensor read after initial boot. cleaned up and improved deep sleeping code.
      added plugin to testing. remove useless value variable
      automaticly updated release notes for v2.0.0-dev6
      automaticly updated release notes for v2.0.0-dev6

Gerald (2):
      HTTP Advanced, enhanced, so that only one http request is sent for one sensor (#156)
      added missing sensor type, to fix problem with i2c soilmoisture sensor... (#157)

Jochen Krapf (1):
      cancel deep sleep loop by pulling the pin GPIO16(D0) to GND (#158)

dzikus (1):
      Added BMP280_CONFIG_SETTING to reduce the temperature of sensor and use oversampling filter (#155)