delay the discovery of sensors after powerup

Calling ow_periodic() from onewire_init() only works when
DEBUG_OW_POLLING is enabled. OW_DEBUG_POLL inside ow_periodic()
delays the discovery for some time and the discovery then works.
Without DEBUG_OW_POLLING, the discovery is not being delayed and
fails for some reason.
To solve this, ow_periodic() will be first called after 50*20ms = 1s.

Signed-off-by: Maximilian Güntner <maximilian.guentner@gmail.com>
Merge pull request #213 from mguentner/1w-discovery-fix

delay the discovery of sensors after powerup
Merge remote-tracking branch 'upstream/master'
Added personal notes
further README.markdown changes
another round, markdown is fun
updated IRMP to rev 120
Merge branch 'master' of github.com:ethersex/ethersex
avrdude config support first working rev, fuses support NIY
Merge branch 'e6_upstream'
document mbr

closes #202

Signed-off-by: Maximilian Güntner <maximilian.guentner@gmail.com>
Merge pull request #221 from mguentner/mbr_docu

document mbr
Merge branch 'e6_upstream'
edit README.markdown
added fuse byte support, fixed argument quotation
Merge branch 'avrdude_config'
News: avrdude_config in master branch
merge branch 'master'